As a motion guide device of this type, there has been known a motion guide device disclosed in Patent Literature 1. This motion guide device includes a track rail and a moving block. The track rail is laid on a fixed portion such as a bed. The moving block is freely movable along the track rail, and is capable of fixing a movable body such as a table being an object to be guided. The moving block is assembled to the track rail through intermediation of a plurality of rolling elements such as balls or rollers. A rolling surface for the rolling elements is formed on the track rail along a longitudinal direction of the track rail. The moving block has a rolling surface for the rolling elements, which is opposed to the rolling surface of the track rail. Further, the moving block has an endless circulation path for allowing the rolling elements to circulate from one end to another end of the rolling surface. Circulation of the rolling elements in the endless circulation path enables the moving block to freely move along the track rail.
Further, a holding belt which is configured to hold the rolling elements at constant intervals is incorporated into the endless circulation path together with the rolling elements. The holding belt is molded from a material having flexibility such as synthetic resin, and pockets configured to receive the rolling elements are arrayed at constant intervals in the holding belt. Further, the holding belt has a total length which is set smaller than a path length of the endless circulation path. Mien the holding belt is incorporated into the endless circulation path, both end portions of the holding belt are opposed to each other with an interval therebetween in the endless circulation path. The rolling elements roll on the rolling surface of the track rail and the rolling surface of the moving block while rotating in the pockets of the holding belt. As the balls circulate in the endless circulation path, the holding belt also circulates in the endless circulation path.
The endless circulation path for the rolling elements in the moving block includes a load path, a return path formed parallel to the load path, and a pair of direction change paths connecting end portions of the load path and the return path to each other. The load path is a region in which the rolling surface of the track rail and the rolling surface of the moving block are opposed to each other. The rolling elements roll in the load path while bearing a load between the track rail and the moving block. Meanwhile, the return path and the pair of direction change paths are no-load paths for returning the rolling elements from a termination end to a start end of the load path. In the no-load paths, the rolling elements do not bear any load.
Therefore, when a relative motion occurs between the track rail and the moving block, the rolling elements in the load path are forcibly caused to roll and proceed in the path. However, the rolling elements in the return path and the pair of direction change paths do not roll themselves, and are pulled or pushed by the rolling elements in the load path through intermediation of the holding belt to proceed in the return path and the pair of direction change paths.